1. Field of the Invention
The present invention generally relates to electronic devices, and more particularly to an electronic device supplied with driving power from an external power source or a built-in battery which is generally detachable.
Recently, there has been considerable activity in the development of portable electronic devices such as portable information processing devices, for example, portable laptop computers which can be easily carried.
The portable computer is supplied with power from a battery. In order to improve the portability, it is required to miniaturize the battery and reduce consumption power.
2. Description of the Related Art
A conventional electronic device is equipped with a suspend/resume function of supplying power to the minimum parts of the device and breaking a supply of power to the other parts thereof so that power consumption can be reduced.
The suspend/resume function is initiated when a suspend/resume button provided to the body of the electronic device is operated. Then, data in progress is saved and power is supplied to the minimum parts necessary to hold the data thus saved. The other parts of the device are in a paused state, so called, suspended state. When the suspend/resume button is operated in the suspended state, the saved data is restored and the original state immediately prior to the suspended state is retrieved.
The suspended state is initiated at the time of carrying the electronic device, so that a reduced amount of power can be consumed in the device.
Generally, the conventional portable computer is designed to handle a functional unit or a module such as a LAN card or a modem card. A connector connected to a telephone line connected to a telephone network or a LAN line connected to a LAN is connected to a modular jack of the computer. In a place in which the connector is available, commercial power source is also available.
The functional unit such as a modem module of a card type (also referred to as a modem card) or a LAN module of a card type (also referred to as a LAN module) can be driven by the built-in battery without a supply of electricity from an external power source obtained via an AC-DC adapter. Hence, even when a supply of power from the commercial source is available, the user is liable to use the built-in battery rather than the commercial source. In this case, the battery is not charged and the driving capability thereof is reduced because the AC-DC adapter is not connected to the electronic device and a supply of power therefrom does not take place.
Particularly, the LAN module has a comparatively high data transmission rate and thus consumes a large amount of energy. Thus, the driving capability of the battery is greatly reduced.
It is a general object of the present invention to provide an electronic device in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide an electronic device in which consumption of power of the built-in battery which is generally detachable.
The above objects of the present invention are achieved by an electronic device comprising: a power supply circuit selectively providing an external power source or an internal power source; a first part determining whether the external power source is selected; a second part detecting a type of a functional unit used in the electronic device; and a third part which controls to supply the functional unit with electricity from one of the external and internal power sources on the basis of determination results obtained by the first and second parts.
A further object of the present invention is to provide a method of controlling a supply of electricity to-a functional unit in which the above-mentioned disadvantages are eliminated.
This object of the present invention is achieved by a method of controlling a supply of electricity to a functional module detachably attached to an electronic device, said method comprises the steps of: determining whether an external power source is selected; detecting a type of a functional unit used in the electronic device; a third part which controls to supply the functional unit with electricity from the external power source or an internal power source on the basis of determination results obtained by the first and second parts.
According to the present invention, the electricity can be supplied from the external power source to the functional module of the given type when the external power is available. Hence, when the internal power source is selected, the functional module is not supplied with electricity therefrom. Hence, it is possible to prevent power from being consumed by the functional module when the external power source is not selected. Of course, as will be seen from the following detailed description, the functional module can be supplied with electricity from the internal power source in response to a given instruction.